Thermal relay



Oct. 14, |924. 1,511,352

A F. H. MILLER THERMAL RELAY Filed June 3, 1920 l, ull',

wlTNEssEs; (3 INVENTOR "d l W AT'TORNEY Patented Oct. 14, 1924.

UNITED STATES 1,511,352 PATENT OFFICE.

FREDERICK H. MILLER, F WILXINSBUYRG, PENNSYLVANIA, ASSIGNOB TO WESTING- HOUSE ELECTRIC MANUFACTURING COMPANY, A CORPORATION OF PEN'NSYL- VANIA.

THERMAL RELAY.

Application illed June 3,

To all 'whom zt may concern:

Be it known that I, FREDERICK H. MILLER, a citizen of the United States, and a resident of Wilkinsburg, in the county I of Allegheny and State of Pennsylvania,

have invented a new and useful Improvement in Thermal Relays, of which the following is a specification.

M invention relates to thermal relays and particularly to thermal relays that embody bimetallic members.

One object of my invention is to provide a relay, of the above-indicated character, that shall have the two elements thereof electrically or thermally insulated from each other.

Another object of my invention is to provide a thermal relay that shall have suiiicient time interval in the operation thereof to effect protection of electrical apparatus against overloads.

Another object of my invention is to provide a thermal relay, of the above-indicated character, that shall embody a bimetallic member in which one of the elements is adapted to be heated to a greater degree than the other elements.

A further object of my invention is to provide a relay, of the above-indicated character, that shall be adapted for use in cartridge-type fuse clips, be relatively inexpensive to construct and be reliable and effective in its operation.

Heretofore, considerable diic-ulty has been encountered in developing suilicient heat ina small bimetallic member, by a current traversing the same, to obtain a movement that was sufficient to effect satisfactory operation of a contact member for controlling an auxiliaryI circuit. This difficulty was due to the fact that the current traversed the two elements in parallel and their resistance was very low.I f

In view of the difficulty of developing sufiicient heat in the bimetallic member for obtaining a movement of predetermined eX- tent, I separate the respective elements and cause the currents to traverse the two elements in series, thus increasing the resistance, and, consequently, the heating of the bimetallic member. By causing the current to traverse only one element of the bimetallic member, a greater degree of heat is ob tained in that element than in the other. A higher temperature in one element eiects a correspondingly greater expansion, and,

1920. Serial No. 386,223.

since the other element has a lower temperature and the two elements are mechanically )oined but thermally insulated, a greater bending force, and, consequently, a movement of greater extent, is obtained.

Figure 1 of the accompanying drawings is a partially diagrammatic and partially sectional view of an electric circuit and an apparatus embodying my invention, and Figs. 2 to 8, inclusive, are mainly sectional views illustrating modifications of the device shown inFig. 1.

A. translating apparatus 1 is adapted tov receive energy from a distribution circuit 2 through a circuit interrupter 3 and is provided with a thermal protective device 4 for lpermitting the interrupter 3 to interrupt the circuit of the translatin apparatus 1 when the temperature of the itter attains or exceeds a predetermined value. The interrupter 3 is provided with an electromagnet 5 for maintaining the interruptor in its closed position and a restraining spring 6 for opening the interrupter when the electromagnet- 5 becomes de-energized. The circuit of the winding of the electromagnet 5 is controlled by the thermal device 4.

The thermal device 4 comprises a cylindrical casing 7 that is provided with a ferrule 8 at one end and a ferrule 9 having an opening 10 therein, at the other end thereof. A supporting member 11 is secured, by a screw 12, to the errule 8 and serves to support a bimetallic member 13 that is secured, at one end thereof, to the supporting member 11. The bimetallic member 13 comprises an element 14 that has a low coefficient of expansion, an element 15 that has a high coefficient of expansion and an insulating element 16 that is dis osed between the two elements 11i an 15. The bimetallic member 13 is provided with a contact member 17, at the movable end thereof, that is adapted to engage a stationary contact member 18 which is mounted upon a supporting member 19. The supporting member 19 is secured, by a screw 20, to an insulating member 21 and thus is maintained out of engagement with the ferrule 9. The supporting member 19 also serves to support one end of the supporting member 11 through an insulating member 22.

The bimetallic member 13 is so supported on the member 11 that the element 15 effects lli) electrical lengagement therewith, whereas the element 14 is both electrically and therheated in accordance with the heating of the` translating apparatus' 1. As the element 15 becomes heated it expands, and, since the element 14 is not heated as rapidly as the element 15, a movement of considerable eX- tent is obtained at the movable end of the bimetallic member and the contract members 17 and 18 become disengaged at a temperature corresponding to a predetermined condition or temperature in the apparatus 1. The winding of the electromagnet 5 is thereby open-circuited and the interrupter 3 is opened by the spring 6.

Fig. 2 of the accompanying drawings illustrates a modification of the device embodying my invention wherein the two ele-` ments 14a and 15 of the bimetallic member 13 are thermally insulated along the length thereof but are joined at one end to permit a current to traverse the two elements in series. greater degree of heat and a correspondingly greater movement may be obtalned in the bimetallic member 13. That is, theresistance of the device is increased, and, consequently, its heating will be. increased.

Fig. 3 of the accompanying drawings 1llustrates a modified form of the device embodying my invention wherein the two members 14" and 15" are connected in series and the member 15 that has'a greater coeflicient of expansion is heat lagged, by the heatinsulating material 27, to increase its temperature. y

Figs. 4 to 8, inclusive, illustratefurther modifications of the device embodying my invention wherein the two elements 14 and 15 are both electrically and thermally insulated from each otherl and wherein only one element 15 is traversed by the circuit current. In the device that is illustrated in Fig. 4, a plurality of magnetizable bands 25 are so disposed as to surround the bimetallic member 13. The hysteresis losses developed in the Vmagnetizable bands 25 serve to increase the temperature of the bimetallic member 13 and thereby to increase the movement elected therein. Fig. 5- is an edge view of a modified form of bimetallic member 13 embodying my invention, wherein the current-carrying element 15 is slotted, as illustrated in Fig. 6, and

prises the two elements.

By means of this arrangement, a v

the other element 14l is employed unslotted, as illustrated in- Fig. 7. By slotting the current-carrying element 15, as illustrated in Fi 6, the crosssectional area is decrease and the effectivelen h and resistance of that member and t e consequent temperature are increased. A greater difference in temperature-is thus developedbetween the two elements 141 and 15 as i1- lustrated in Figs. 6` and 7, respectively, and a correspondingly larger movement,is obtained in the bimetallic member 13 that com- Fig. 8 of the accom' anying drawings illustrates a further mo viication wherein the element 15 that has a high coeilicient` of expansion is traversed by the circuit current and the other element 14 that has a low -coeilicient of expansion is provided with metallic radiating fins 26 to provide a greater thermal-storage capacity'and thereby decrease the resulting temperature of that element.

While I have shown a preferred form and several modifications of a device embodying my invention, I do not limit my invention to the speciiic structure of the preferred form that is illustrated, since the various modilications that are illustrated may be made therein within thespirit `and scope of the invention as set forth in the appended claims. Y

I claim as myinvention 1. A thermal relay comprising. a' heatresponsive device consisting ofl two elements having `different coeiiicients of expansion, one element only of which is adapted to Vbe heated. A

2. A thermal-responsiverelay comprising two elements having diierent 'heat-storage capacities. f

3. A thermal relay comprising two elements mechanically joined along their length and thermally insulated.v

4. A thermal relay for an electricy circuit comprising two metallic elements havin dili'erent coeiicients of expansion one on y of which may be traversed by the circuit current. y

A bimetallic thermal relay for an electric circuit comprising two elements having diderent coeiiicients of e ansion, the two elements being mechanical y joined and one f of the elements being thermally insulated to permit an increase in its temperature and, consequently, in the bending eii'ort caused by unequal expansion when subjected to the circuit current.

6. A bimetallic thermal lrelay for an electric circuit comprising two elements having different coefficients of expansion, one of the elements serving as a conductor for the circuit current and being so thermally insulated as to reproduce predetermined thermal conditions correspondingto predetermined values of current in the circuit and, consequently, a corresponding diferential movelnent between said elements.

7. In an electric circuit, the combination with a translating device, of a bimetallic thermal device for reproducin the temperature conditions in the trans ating device comprising two mechanically-'oined elements thermally insulated and aving dlfferent coefficient of expansion.

8. In an electric circuit, the combination with a translating device and a circuit interrupter, of means for precluding a rise in the temperature of the translating devlce above a predetermined value comprising two thermally-responsive mechanically-joined elements thermally insulated from each other having different coeiicients of expansion, one of which members is traversed by the circuit current, means for actuating the interrupter, and a fplurality of contact members engagement o which is controlled by the thermal-responsive means for controlling the circuit of the interrupter ac-l tuating means.

9. A thermal relay for electrical apparatus comprising an enclosing casing, connecting terrules at the ends thereof, a bimetallic member comprisin two mechanicallyjoined elements therma ly insulated from cach other and having different coefficients ot' expansion and connecting means for the terrules, said means being controlled by the bimetallic member.

10. A thermal relay for electrical apparatus comprising an enclosing casing, connecting ferrules at the ends thereof, a bimetallic member comprising two mechanically-joined elements thermally insulated from each other and having different coeicients of ex- `pansion, one only of the elements serving as a conducting means between the two ferrules.

11. A thermal relay for an electric circuit containing electrical apparatus comprising an enclosing casing, two thermal-responsive elements having different coeiicients of eX- pansion, one of which is connected in circuit with the apparatus and means controlled by the relay for disconnecting the apparatus from the circuit when predetermined conditions obtain in the apparatus.

12. A thermal relay for controlling the automatic disconnection of an electrical apparatus from an electric circuit when a predetermined temperature is developed in the apparatus comprising two thermally-responsive thermally-insulated elements having diierentcoefficients of expansion and means controlled by the co-operation of the two elements for effecting the disconnection oi the apparatus.

13. A thermal relay for controlling the automatic disconnection of an electrical apparatus from an electric circuit when a predetermined temperature is developed in the apparatus com rising two thermally-responsive therma ly-insulated elements having different thermal-storage capacities and means controlled b the co-operation of the two elements for e ecting the disconnection of the apparatus.

14. A thermal relay for controlling the automatic disconnect-ion of an electrical apparatus from an electric circuit when a predetermined temperature is develo ed in the apparatus comprising two therma y-responsive thermall -insulated elements havin different coeiii'cients of ex ansion, one o which is connected in circuit with the electrical apparatus to be heated in accordance therewith and means controlled by the cooperation of the two elements for effecting the disconnection of the apparatus.

15. A thermal relay comprising two elements secured to elect a dilerential movement at one end thereof and means for effecting a greater degree of heating in one element than in the other by an electric current traversing the same.

16. A thermal relay comprising an enclosing casing, connecting ferrules at the ends thereof, two thermally-res onsive thermally-insulated elements having different coefficients of expansion and a contact member controlled by one of the elements.

17. A thermal relay comprising an enclosin casing, connecting ferrules at the ends t ereof, two thermally-responsive thermally-insulated elements having different coeiicients of expansion one element only of which serves as a conducting means between the ferrules and a contact member controlled by one element.

18. A thermal relay comprising two thermally-responsive elements having different coefficients of expansion xedly mounted at one end, mechanically joined to produce a turning force at the other end, one of the elementslbeing heat-insulated from the other to produce a greater temperature therein and a correspondingly greater turning force, when subjected to an electric current.

19. A thermal-responsive device comprising two elements having different coeicients` of expansion and means for permitting one element to be heated to a greater degree than the other, when traversed by an electric current.

20. The method of obtaining a magnified movement in a bimetallic member which consists in insulating the two elements from each other, heating one element and heatlagging one element to control the dissipation of heat therefrom.

21. In a bimetallic member, the combination with the two metallic elements and insulating means therebetween, of means for securing the elements along the length thereof to preclude any lost motion therebetween.

10 to effect a diferentia'l expansion movement i therein and means for heating one only of e ysaid. A`elements.

A thermal-responsive member comprismg two elements of diierent coecients of expansion mechanicallyseeured together '15j lto eect a differential expansion movement,"`

therein and means for aectin the temperature of each of v:said elementsmdependently Y of the other.

\ In testimony whereof, I lieve hereuntofzo 'l slglcribed my name this 27th,"day of May FREDERICK. Hg MILLER'. 

